Portable instant hot water heater

TECHNICAL FIELD OF THE INVENTION

00002The present invention is directed to an instant hot water heater, and more specifically, a portable instant hot water heater.

BACKGROUND OF THE INVENTION

00003Camping and tailgating are popular recreational activities enjoyed by many. Some people camp so that they may enjoy the outdoors, and others use camping as an inexpensive alternative to staying in hotels. Tailgating is a great way to meet and eat before ball games, and has become quite the ritual for many season ticket holders.

00004Although many campers enjoy being in the outdoors, often campers like to enjoy the luxuries of home while camping. For example, many campers bring lounge chairs or hammocks, portable air mattresses or cots, and similar items to make a camping experience more comfortable. Similarly, people often like to enjoy home luxuries while tailgating.

00005One item that most campers and tailgaters have to learn to do without is the availability of hot water. Most homes are equipped with running hot water, supplied by a hot water heater that is connected with the home plumbing. The user simply turns on a faucet, and after a short delay, hot water is supplied. The hot water may be used for bathing, cleaning, cooking, or washing clothes.

00006In a camping or tailgating environment, if a user desires hot water, the user must obtain water, for example, from a faucet or other water source, and place the water in a container over a fire, such as a camp stove or an open fire. The water must then be heated to a desired temperature. This process typically takes several minutes, and water temperatures that are obtained using this process are relatively imprecise. The water that has been heated is hard to dispense because it is in a heated pot and the pots often are not designed for pouring. Also, if a user desires a lot of heated water, the process must be repeated until enough hot water is produced. Moreover, a user risks overheating the water to a point where it is dangerous to handle, especially for children.

00007In practice, because the process for preparing and obtaining heated water is so difficult when camping or tailgating, most users typically wash dishes, prepare food, and wash their face and hands with unheated water. Typically, the users will heat water only as necessary for food preparation and for making instant coffee and tea, for example.

SUMMARY OF THE INVENTION

00008The present invention provides an instant water heater that utilizes a flame, for example, produced by a propane burner. The instant hot water heater is fully portable, and may be used, for example, in camping or tailgating environments. The instant hot water heater is configured to deliver varying degrees of hot water, for example ranging from 90° to 150°, instantaneously. The hot water heater is designed to operate regardless of the temperature of source water. Hot water from the instant hot water heater may be used for many applications, including but not limited to, washing dishes, food preparation, making coffee and tea, and washing face and hands.

00009Water is delivered to a base unit of the instant hot water heater by a pump that is attached to the base unit by a hose. The pump may draw water from a reservoir or other water source. Alternatively, water may be provided by a conventional hose or another water source.

00010The base unit includes a burner and a fuel source, such as a propane cylinder. A conventional igniter, such as is used for propane lanterns, may be provided for lighting a flame in the burner.

00011The pump delivers water to the base and into and through a flow control valve. From the flow control valve, the water flows into a pre-heater and then into a heat exchanger. The pre-heater includes a structure that wraps around a base of the burner and that is heated by the burner. This structure heats the water prior to the water entering the heat exchanger, increasing efficiency of the water heating process, and reducing the possibility of condensation being formed at the heat exchanger.

00012The heat exchanger is heated by the burner, and the water flows through coils that are embedded in the heat exchanger. Water exiting the heat exchanger is heated to a temperature that is ready for use.

00013Water exits the base unit through an outlet spout that resembles a kitchen faucet spout. The spout swings out from the base unit to dispense water. The spout may be stored and locked into position in a handle for the base unit, and may be swung out for use.

00014A flow control system controls the amount of water flowing through the base unit so that the water may be heated to a desired level for a user. By lowering the flow of water through the heat exchanger, the water has more time to absorb heat and to get hotter.

00015The base unit includes a single control knob that turns on the pump and the burner and operates the flow control valve. In a first portion of movement of the control knob (e.g., a first quarter-turn of the control knob), the pump and a control circuit for the base unit are turned on. In a second portion of movement of the control knob (e.g., a second quarter-turn of the control knob), the burner is turned on. Further movement in the second portion adjusts the output of the burner. The burner reaches full output at the end of the second portion. At a third portion of movement of the control knob (e.g., a third quarter-turn of the control knob), the burner remains at the highest output setting, but the flow control valve is adjusted to reduce the flow of water. The reduced flow of water allows the water to absorb more heat, raising the temperature of the water. In this manner, adjusting the single control knob provides a range of temperatures for the output water depending upon how much the handle has been turned.

00016The base unit also includes an over temperature circuit that has a sensing element and a solenoid. The sensing element, which may be a thermistor, sends a signal to the solenoid as a result of the water exceeding a particular temperature. This condition may occur, for example, if water is no longer being supplied by the pump (i.e., the reservoir is empty.) As a result of the signal, the solenoid shuts off fuel to the burner, preventing boiling water from exiting the spout. Other safety devices may be employed, such as a device for sensing the tilt of the base unit and shutting off the burner as a result of too much tilt, a flow sensing switch that shuts off the burner if there is no or low water flow, or a flame control that senses the presence of a flame in the burner, and absent such a flame, cuts fuel to the burner.

00017The instant hot water heater of the present invention is fully portable, and may be used in remote locations, such as for camping or for tailgating. Its function and operation are very easy to understand, and setting up the unit takes a minimal amount of time.

00018Other advantages will become apparent from the following detailed description when taken in conjunction with the drawings, in which:

BRIEF DESCRIPTION OF THE DRAWINGS

00019<figref idref="DRAWINGS">FIG. 1</figref> is an isometric view showing an instant hot water heater in accordance with the present invention, with a spout for a base unit of the instant hot water heater extending outward, and a pump for the instant hot water heater connected to a water reservoir;

00020<figref idref="DRAWINGS">FIG. 2</figref> is a front right isometric view of the instant hot water heater of <figref idref="DRAWINGS">FIG. 1</figref>, showing the pump and the spout in storage positions;

00021<figref idref="DRAWINGS">FIG. 3</figref> is a front right, isometric view of the instant hot water heater of <figref idref="DRAWINGS">FIG. 1</figref>, with parts removed for detail;

00022<figref idref="DRAWINGS">FIG. 4</figref> is a rear right, isometric view of the instant hot water heater of <figref idref="DRAWINGS">FIG. 1</figref>, with parts removed for detail;

00023<figref idref="DRAWINGS">FIG. 5</figref> is a right front, isometric view of the some internal components of the instant hot water heater of <figref idref="DRAWINGS">FIG. 1</figref>;

00024<figref idref="DRAWINGS">FIG. 6</figref> is a left front, isometric view of the instant hot water heater of <figref idref="DRAWINGS">FIG. 1</figref>, with parts removed for detail;

00025<figref idref="DRAWINGS">FIGS. 7-10</figref> are diagrammatic representation of a cross-section of a control knob for use with the instant hot water heater of <figref idref="DRAWINGS">FIG. 1</figref>, the figures showing various stages of rotation of the control knob; and

00026<figref idref="DRAWINGS">FIG. 11</figref> is a schematic drawing of controls for the present invention.

DETAILED DESCRIPTION

00027In the following description, various aspects of the present invention will be described. For purposes of explanation, specific configurations and details are set forth in order to provide a thorough understanding of the present invention. However, it will also be apparent to one skilled in the art that the present invention may be practiced without the specific details. Furthermore, well-known features may be omitted or simplified in order not to obscure the present invention.

00028Referring now to the drawings, in which like reference numerals represent like parts throughout the several views, <figref idref="DRAWINGS">FIG. 1</figref> shows an instant hot water heater <b>20</b> in accordance with the present invention. The instant hot water heater includes a base unit <b>22</b> attached by a hose <b>24</b> to a pump <b>26</b>. In the embodiment shown, the pump <b>26</b> is attached to a reservoir <b>28</b>. A wire <b>30</b> extends between the pump <b>26</b> and the base unit <b>22</b> for providing power to the pump. For the embodiment shown, a coupling <b>32</b> is provided at a distal end of the pump <b>26</b> for attaching the pump <b>26</b> to the reservoir <b>28</b>.

00029In operation, as further described below, the pump <b>26</b> draws water from the reservoir <b>28</b> through the hose <b>24</b> and into the base unit <b>22</b>. The base unit <b>22</b> heats the water and provides the heated water at an outlet, for example, a spout <b>42</b>.

00030To store the instant hot water heater <b>20</b>, as shown in <figref idref="DRAWINGS">FIG. 2</figref>, the hose <b>24</b> may be wrapped around the bottom portion of the base unit <b>22</b>, and the pump <b>26</b> may be snapped onto a snap ring <b>33</b>. The spout <b>42</b> is pressed into a handle <b>40</b> for the base unit <b>22</b>, as is further described below.

00031The pump <b>26</b> and the reservoir <b>28</b> may alternatively be replaced by a conventional water hose or another water source that provides a flow of water. If a water hose is used, a regulator or other flow control device may be needed to control the flow of water into the base unit.

00032The base unit <b>22</b> includes left and right outer casings <b>34</b>, <b>36</b> that fit together in a clam shell fashion. The right outer casing <b>36</b> is shown removed in <figref idref="DRAWINGS">FIG. 3</figref> so that details of the internal components of the base unit <b>22</b> may be seen.

00033Vents <b>38</b> (<figref idref="DRAWINGS">FIG. 2</figref>) are provided outside of the base unit <b>22</b> for allowing heat to escape the unit. The handle <b>40</b> is integrated into the top portion of the base unit. The handle <b>40</b> extends horizontally along the top of the base unit <b>22</b>, and is attached at front and rear sections of the base unit. The spout <b>42</b> may be stored in a cavity that extends the length of the handle. The spout <b>42</b> is hollow and is rotatably mounted at one end to the base unit <b>22</b>. As can be seen in <figref idref="DRAWINGS">FIG. 1</figref>, the spout may be rotated out so that it is accessible for dispensing heated water from the base unit <b>22</b>.

00034A control knob <b>44</b> is located on the front of the base unit <b>22</b>. The control knob <b>44</b> is configured so that it controls operation of the instant hot water heater <b>20</b>. As further described below, the control knob <b>44</b> is capable of turning on the pump <b>26</b> and other components of the instant hot water heater, and controlling the water output temperature of the base unit <b>22</b>.

00035Turning now to <figref idref="DRAWINGS">FIG. 3</figref>, a propane tank <b>46</b>, such as a 16.4 oz. COLEMAN brand propane cylinder, is mounted inside the base unit <b>22</b>. The propane tank <b>46</b> is threaded into the bottom of a regulator <b>48</b>. The regulator <b>48</b> controls the flow of fuel from the propane tank <b>46</b> to a solenoid valve <b>50</b>. The regulator <b>48</b> includes female threads (not shown) for fitting onto the threaded top of the propane tank <b>46</b>. The regulator <b>48</b> is designed in a manner known in the art to control the amount of propane exiting the propane tank <b>46</b>. Fuel released by the regulator <b>48</b> flows through the solenoid valve <b>50</b> to a burner <b>52</b>, best shown in FIG. <b>5</b>. The burner <b>52</b> provides the flame for a heat exchanger assembly <b>54</b> (FIG. <b>3</b>).

00036The solenoid valve <b>50</b> is in a normally open position, and is connected to a printed circuit board <b>70</b>. The printed circuit board <b>70</b> includes necessary controls to instruct the solenoid valve <b>50</b> to close, as further described below.

00037The burner <b>52</b> includes burner rings <b>72</b> (FIG. <b>5</b>). Extra burner rings <b>72</b> may be provided to provide a higher Btu output and to keep noise level to a minimum. For example, the burner rings <b>72</b> may be stacked 3 times higher than in a conventional camp stove so as to allow higher heat output.

00038A pre-heater assembly <b>74</b> is provided that is attached to the burner <b>52</b>. The pre-heater assembly <b>74</b> includes a copper plate <b>76</b> that is placed between the burner rings and a burner base <b>77</b>. Although described as copper, the copper plate <b>76</b> may be formed of another suitable conductive material.

00039The copper plate <b>76</b> is surrounded by conductive tubing <b>78</b>. The conductive tubing <b>78</b> may be, for example a ⅜″ diameter copper tube.

00040The heat exchanger assembly <b>54</b> includes sides <b>80</b> (<figref idref="DRAWINGS">FIGS. 3 and 4</figref>) that extend up and around the burner <b>52</b>. A heat exchanger <b>82</b> having heating fins is mounted at the top of the sides <b>80</b>. An upper heating shield <b>84</b> extends over the heat exchanger <b>82</b>. A lower heating shield <b>86</b> extends around a bottom of the heat exchanger assembly <b>54</b> and under the burner <b>52</b>.

00041The routing of the conductive tubing <b>78</b> is shown in FIG. <b>5</b>. The walls of the heat exchanger assembly <b>54</b> and the fins of the heat exchanger <b>82</b> have been removed to show detail. One end of the conductive tubing <b>78</b> extends from the pre-heater assembly <b>74</b> around the walls or sides <b>80</b> of the heat exchanger assembly <b>54</b> (shown wrapping around these walls in <figref idref="DRAWINGS">FIGS. 3 and 4</figref>) and into the heat exchanger <b>82</b>. The conductive tubing <b>78</b> then makes a circuitous path through the heat exchanger <b>82</b>, as best shown in FIG. <b>5</b>. An end of the conductive tubing <b>78</b> extends into the bottom of the spout <b>42</b>.

00042The opposite end of the conductive tubing <b>78</b> that leads from the pre-heater assembly <b>74</b> extends to a flow control valve <b>90</b> (best shown in FIG. <b>6</b>). The flow control valve <b>90</b> is mounted to receive water from the pump <b>26</b> via the hose <b>24</b>. The flow control valve <b>90</b> is in a normally open position and includes a rocker arm lever <b>92</b>. A push rod <b>94</b> is connected to the rocker arm lever <b>92</b>. The flow control valve <b>90</b> also includes a return spring (not shown, but known in the art) for biasing the flow control valve <b>90</b> in the open position and a low flow stop (also not shown) to prevent complete closure of the flow control valve <b>90</b>.

00043Details of the control knob <b>44</b> can be seen in FIG. <b>5</b>. The control knob <b>44</b> includes an outer knob <b>100</b> and an inner knob <b>102</b>. The outer knob <b>100</b> is mounted over and around the inner knob <b>102</b>. The inner knob <b>102</b> is mounted on a regulator shaft <b>104</b> for the regulator <b>48</b>. A torsion spring <b>106</b> fits between the inner knob <b>102</b> and the outer knob <b>100</b>. The torsion spring <b>106</b> fits into a pocket (not shown) in the rear of the outer knob <b>100</b>. Spring clip ends <b>110</b> of the torsion spring <b>106</b> fit into holes <b>112</b> on the inner knob <b>102</b> and outer knob <b>100</b> (the hole on the back of the outer knob is not shown, but is similar to the hole <b>112</b>), respectively.

00044A gap <b>114</b> (<figref idref="DRAWINGS">FIGS. 7-10</figref>) is defined between the inner sidewall of the outer knob <b>100</b> and the outer sidewall of the inner knob <b>102</b>. An end of a flow valve lever <b>116</b> (shown in full in <figref idref="DRAWINGS">FIG. 6</figref>, and a cross section of the end of which is shown in <figref idref="DRAWINGS">FIGS. 7-10</figref>) extends into the gap <b>114</b> between the inner knob <b>102</b> and the outer knob <b>100</b>. The flow valve lever <b>116</b> is pivotably mounted to the base unit <b>22</b>, for example to a side of the regulator <b>48</b>. A forward end of the flow valve lever <b>116</b> extends outward toward the control knob <b>44</b> and bends at a first angle and then at a second angle so as to straighten back parallel to the rest of the flow valve lever <b>116</b>. This end of the flow valve lever <b>116</b> is seated in the gap <b>114</b> between the inner knob <b>102</b> and the outer knob <b>100</b>. The opposite end of the flow valve lever <b>116</b> is attached to the push rod <b>94</b> that in turn is attached to the rocker arm lever <b>92</b> of the flow control valve <b>90</b>.

00045A protrusion <b>118</b> (<figref idref="DRAWINGS">FIGS. 7-10</figref>) is fixed on the inside surface of the outer knob is located in the gap between the outer knob <b>100</b> and the inner knob <b>102</b>. When the control knob <b>44</b> is in a normally closed position, the protrusion <b>118</b> is located approximately halfway around the outer knob <b>100</b> from the flow valve lever <b>116</b>. The function of the protrusion <b>118</b> is described further below.

00046A battery <b>120</b> is mounted in the base unit <b>22</b>. The battery <b>120</b> is connected to the printed circuit board <b>70</b>, the pump <b>26</b>, an ignition module <b>124</b> (<figref idref="DRAWINGS">FIG. 11</figref>) for the burner <b>52</b>, and the solenoid valve <b>50</b>. If desired, the battery may include an integral or connected battery charger <b>128</b> (FIG. <b>11</b>). If so, an AC connector port <b>126</b> may be supplied on the outer shell of the base unit <b>22</b> for supplying power to the battery charger.

00047Operation of the instant hot water heater <b>20</b> may be understood with reference to the previous description and the circuit diagram at FIG. <b>11</b>. To set up the instant hot water heater <b>20</b>, a user disconnects the pump <b>26</b> from the snap ring <b>33</b> and unwinds the hose <b>24</b> from around the bottom of the base unit <b>22</b>. The coupling <b>32</b> on the pump <b>26</b> is attached to a water source, such as the reservoir <b>28</b>. Preferably, the instant hot water heater <b>20</b> is placed on a level surface. By doing so, a flame in the burner <b>52</b> extends upward to the heat exchanger <b>82</b>, and there is no risk of overheating the wrong components in the instant hot water heater <b>20</b>. To this end, a tilt sensor or switch <b>130</b> (<figref idref="DRAWINGS">FIG. 11</figref>) may be provided that is in a normally closed position, and that when the base unit <b>22</b> is not within a particular range of being level (e.g., +/−30 degrees), the switch is closed.

00048In any event, after the base unit <b>22</b> and the pump <b>26</b> are ready, the user rotates the spout <b>42</b> out of the handle <b>40</b>. If desired, a detente <b>132</b> (<figref idref="DRAWINGS">FIG. 3</figref>) or other catch may be provided on the end of the spout <b>42</b> for fitting into a gap <b>133</b> on the handle <b>40</b>. The spout may otherwise be temporarily locked into the handle <b>40</b>. To permit the spout <b>42</b> to rotate without breaking the connection of the spout with the tubing <b>78</b>, the spout <b>42</b> may be mounted on an appropriate rotator piece <b>134</b> (FIG. <b>4</b>). Rotating connections that allow fluid to flow therethrough are well known, and a detailed description is not provided here so as not to obfuscate the invention. However, in one embodiment, the rotator piece <b>134</b> may be fixed to the spout <b>42</b>, and the tubing <b>78</b> below the spout may be flexible. The spout <b>42</b> rotates within a slot <b>136</b> on the outside of the base unit <b>22</b> until it extends outward as shown in FIG. <b>1</b>.

00049After the spout <b>42</b> has been rotated outward, the user actuates the control knob <b>44</b> by grasping the outer knob <b>100</b> and rotating it counterclockwise. A sequence of different stages of movement of the control knob <b>44</b> is shown in <figref idref="DRAWINGS">FIGS. 7-10</figref>. In the first half turn of the outer knob <b>100</b> (movement from <figref idref="DRAWINGS">FIG. 7</figref>, through <figref idref="DRAWINGS">FIG. 8</figref>, to FIG. <b>9</b>), the inner knob <b>102</b> turns with the outer knob <b>100</b>. The flow valve lever <b>116</b> does not move during this rotation, but instead stays stationary in the same position within the gap <b>114</b>. In the first quarter of the movement (<figref idref="DRAWINGS">FIG. 7</figref> to FIG. <b>8</b>), a switch <b>138</b> (<figref idref="DRAWINGS">FIG. 11</figref>) in the regulator shaft <b>104</b> turns on the pump <b>26</b> and the printed circuit board <b>70</b>.

00050During the first two portions of the movement of the control knob <b>44</b> (i.e., in the embodiment described, movement from <figref idref="DRAWINGS">FIG. 7</figref> to FIG. <b>9</b>), water flows unimpeded through the flow control valve <b>90</b>. In the first quarter of a turn, the water flows through without being heated. A user will usually move quickly through this portion of movement of the control knob to the second portion. Continued movement of the outer knob <b>100</b> past the first quarter turn and into the second portion of movement (i.e., beyond <figref idref="DRAWINGS">FIG. 8</figref> toward <figref idref="DRAWINGS">FIG. 9</figref>) begins a supply of gas via the regulator <b>48</b> to the burner <b>52</b> and causes the ignition module <b>124</b> to fire.

00051Although the function, structure, and operation of the regulator <b>48</b> and the ignition module are generally known, a general description is given here for the convenience of the reader. To start combustion in the burner <b>52</b>, the control knob <b>44</b> is rotated, in this case in a counterclockwise direction, causing the regulator shaft <b>104</b> to rotate. Rotation of the regulator shaft <b>104</b> causes two things to happen. First, the rotation of the regulator shaft <b>104</b> opens a valve (not shown), permitting the release of propane from the propane tank <b>46</b> and into the burner <b>52</b>. Second, rotation of the regulator shaft <b>104</b> causes the ignition module <b>124</b> to spark. The spark ignites the propane in the burner <b>52</b>, causing combustion.

00052Turning the control knob <b>44</b> further counterclockwise in the second portion of movement (i.e., from <figref idref="DRAWINGS">FIG. 8</figref> to <figref idref="DRAWINGS">FIG. 9</figref>) opens the valve even more, and increases the amount of propane supplied by the propane tank <b>46</b>, thus increasing the size of the flame in the burner <b>52</b>. Likewise, clockwise rotation of the control knob <b>44</b> while there is a flame in the burner <b>52</b> decreases the size of the flame. This flame adjustment may be used to increase or decrease the heat supplied to the heat exchanger assembly <b>54</b>.

00053In the second quarter of a turn, the heat exchanger assembly is heated to the extent of the flame size in the heat exchanger assembly <b>54</b>. Water flowing through the base unit <b>22</b> is heated by the heat exchanger assembly. The water flows from the flow control valve <b>90</b> through the conductive tubing <b>78</b> and around the copper plate <b>76</b>. As the water flows around the copper plate <b>76</b>, it is preheated before entering the heat exchanger <b>82</b>. This preheating of the water prior to it entering the heat exchanger <b>82</b> increases the efficiency of heating of water by the heat exchanger assembly <b>54</b> and reduces the likelihood of condensation being formed as a result of heating the water. The conductive tubing <b>78</b> extending around the sides <b>80</b> of the heat exchanger assembly <b>54</b> provides additional heating of the water before it enters the heat exchanger <b>82</b>, increasing the efficiency of the system.

00054In addition to the preheating effect provided by the copper plate <b>76</b>, the copper plate minimizes radiated heat on the bottom of the base unit <b>22</b>. The lower heat shield also enhances protection of the bottom of the base unit <b>22</b>.

00055A user may find that water exiting the spout <b>42</b> is sufficiently heated when the control knob <b>44</b> is in the second range of movement (i.e., between FIG. <b>8</b> and FIG. <b>9</b>). In this range of movement, the user may continue to rotate the knob in the counterclockwise direction, and doing so increases the burner flame, and the heat provided to the heat exchanger assembly <b>54</b> and the water flowing through the heat exchanger assembly. At the end of the second range of movement, the flame is at its maximum heat output, because the inner knob <b>102</b> cannot rotate any further because the regulator shaft <b>104</b> has hits the end of its range of rotation.

00056If the user wishes to increase the heat of the water even more, the user may continue to rotate the outer knob <b>100</b> past the half turn (i.e., counterclockwise beyond FIG. <b>9</b>). Although the inner knob <b>102</b> cannot rotate any further, the user may continue to rotate the outer knob <b>100</b> against the action of the torsion spring <b>106</b>. Simultaneous to the beginning of this movement, the protrusion <b>118</b> on the inside of the outer knob <b>100</b> engages the end of the flow valve lever <b>116</b> and begins to press it downward, driving the opposite end of the flow valve lever <b>116</b> upward, along with the push rod <b>94</b>. When the push rod <b>94</b> is driven upward, the rocker arm lever <b>92</b> of the flow control valve <b>90</b> is also driven upward. This movement of the rocker arm lever <b>92</b> causes the flow control valve <b>90</b> to begin to restrict the flow of water into the base unit <b>22</b>. The continued rotation of the outer knob <b>100</b> drives the end of the flow valve lever <b>116</b> down even further, from the position in <figref idref="DRAWINGS">FIG. 9</figref> toward the position in <figref idref="DRAWINGS">FIG. 10</figref>, further closing the flow control valve <b>90</b>. This movement may continue, for example for a 45 degree turn of the outer knob <b>100</b>, until the flow control valve <b>90</b> reaches the low flow stop.

00057By decreasing the flow of water into the base unit <b>22</b>, the amount of water that is heated by the heat exchanger unit <b>54</b> is decreased. Thus, the heat that is transferred per unit water is increased. As such, the temperature of the water exiting the spout <b>42</b> is increased. Although the volume of the water over a defined increment of time exiting the spout <b>42</b> would be decreased, the temperature of that water would be higher.

00058In summary, the control knob <b>44</b> provides several operations for the base unit <b>22</b> and the pump <b>26</b>. A first portion of movement of the control knob <b>44</b> (in this embodiment, the first quarter turn) causes the pump <b>26</b> and the printed circuit <b>70</b> to be powered on. A second portion of the movement of the control knob <b>44</b> (in this embodiment, the second quarter turn) causes the burner <b>52</b> to be lit and adjust the length or output of the flame in the burner. A third portion of movement of the control knob <b>44</b> (e.g., a 45 degree turn after the first 90 degrees of motion) decreases the flow of water through the heat exchanger assembly <b>54</b>, thus increasing the temperature of the water without adding additional heat output. The three different functions for the control knob <b>44</b> may be performed by more than one control, or may be performed by a single control that performs one or more of these operations in a different manner. For example, the first portion may be provided by pushing a control knob inward, the second portion by rotating the knob, and a third portion by continued rotation of the knob or movement of the knob downward. However, the described control knob <b>44</b> is advantageous in that using the same movement (i.e., rotation of the knob) a user may turn on the instant hot water heater and may be provided a desired temperature of water, without knowing how the operation has occurred, or, if the user turns the control knob into the third portion, that the flow of water has been limited. Other single movement control mechanisms may be used, such as by having a control knob that portions of movement in one direction (e.g., downward) performs each of the three portions of operation for the instant hot water heater <b>20</b>.

00059In the embodiment shown, the second portion of operation by the control knob <b>44</b> provides a temperature delta of approximately 55° F. between inlet temperature of water and outlet temperature of water at the spout <b>42</b>. Thus, if water enters the base unit <b>22</b> at 65° F., the outlet temperature of the water at spout <b>42</b> would be approximately 110° F. If warmer water temperature is desired, the water flow must be reduced. As described above, this operation is accomplished by turning the outer knob <b>100</b> into the third portion of operation of the control knob <b>44</b>, which reduces the flow of water. The low flow stop prevents the flow of water from being so low that the unit would overheat.

00060If desired, an over temperature control, such as a 170° F. over temperature control <b>140</b> (<figref idref="DRAWINGS">FIG. 8</figref>) may be provided. The over temperature control <b>140</b> may use a temperature sensing element, such as a thermistor to sense overheating of the heat exchanger assembly <b>54</b>. The over temperature control <b>140</b> may alternatively sense the temperature of water exiting the spout <b>42</b>. The over temperature control <b>140</b> is in a normally closed position, and exceeding an upper limit (e.g., 170° F.) causes the control to open. If desired, an over temperature LED <b>142</b> may be provided that is lit when the over temperature control opens to shut off the propane gas valve <b>50</b>.

00061Other controls may be provided to protect the base unit <b>22</b>. For example, a no flame control <b>144</b>, a low voltage control <b>146</b>, and a flow sensing switch <b>148</b> may all be provided for safety of the base unit <b>22</b>. The flow sensing switch <b>148</b> may determine whether an adequate supply of water is flowing through the base unit <b>22</b>, the low voltage control <b>146</b> may determine whether there is adequate voltage to operate the base unit <b>22</b> and the pump <b>26</b>, and the no flame control <b>144</b> may sense whether a flame is operational in the heat exchanger unit <b>54</b>. For the diagram shown in <figref idref="DRAWINGS">FIG. 11</figref>, each of these switches is in a normally closed position, and opening the switch causes the propane gas valve <b>50</b> to close, shutting off flow of gas to the burner <b>52</b>. If desired, one or more LEDs, such as a low voltage LED <b>150</b> may be provided for indicating conditions of the base unit <b>44</b>.

00062The printed circuit board <b>70</b> may include the necessary control components to operate the functions of the instant hot water heater <b>20</b>. The printed circuit board <b>70</b> may be alternatively be standard control (i.e., a device or mechanism used to regulate or guide the operation of a machine, apparatus, or system), a microcomputer, or any other device that can execute computer-executable instructions, such as program modules. Generally, program modules include routines, programs, objects, components, data structures and the like that perform particular tasks or implement particular abstract data types. A programmer of ordinary skill in the art can program or configure the printed circuit board <b>70</b> to perform the functions described herein.

00063In the described embodiment, it takes about three seconds for heated water to come out of the spout <b>42</b> after a user begins operation of the instant hot water heater <b>20</b>. There is control of the water temperature that exits the spout <b>42</b> from inlet temperature to approximately 150° F. To provide this heat of water, the regulator is adjustable from zero fuel to 30,000 Btus. In addition, the flow control valve <b>90</b> is adjustable from one gallon per minute to ¼ gallon per minute.

00064For the described embodiment, a single 16 oz. propane cylinder can produce around 40 gallons of heated water, assuming the flow control valve <b>90</b> is not limiting the flow of water. If desired, a user may connect the base unit <b>22</b> to a 20 lb. propane cylinder with a hose so that extended use may be provided.

00065The instant hot water heater <b>20</b> provides varying degrees of hot water instantaneously. The instant hot water heater <b>20</b> can be transported and may be used in all locations, such as for camping or tailgating, and may be used for many applications including washing dishes, food preparation, making coffee and tea, and washing face and hands.

00066Other variations are within the spirit of the present invention. Thus, while the invention is susceptible to various modifications and alternative constructions, a certain illustrated embodiment thereof is shown in the drawings and has been described above in detail. It should be understood, however, that there is no intention to limit the invention to the specific form or forms disclosed, but on the contrary, the intention is to cover all modifications, alternative constructions, and equivalents falling within the spirit and scope of the invention, as defined in the appended claims.